1. Field of the Invention
The present invention relates to a wheel cover for automobiles, including a substantially dish-like main body which is composed of a thermoplastic synthetic resin material.
2. Description of the Related Art
Wheel covers for automobiles are often subjected to severe impact forces, particularly when struck by pebbles during driving on unpaved road. Thus, in order to realize wheel covers with improved rigidity and impact resistance, the main body of the wheel cover is generally provided on its rear surface with a plurality of reinforcing ribs formed integrally with and projecting axially rearwardly from the main body.
It is well known in the art that higher rigidity and impact resistance of the wheel cover can be achieved by increasing the section modulus of the reinforcing ribs, e.g. by increasing the width of the rib at its bottom portion adjacent to the rear surface of the main body. On the other hand, however, provision of the reinforcing ribs with an increased width of the bottom portion suffers from serious problems. Among others, due to a relatively uneven distribution of the molten synthetic resin material in an injection mold cavity in which the wheel cover is molded, an undesirable sink mark tends to appear on the front surface of the wheel cover as being clearly visible from outside, thereby significantly deteriorating the appearance of the product. Consequently, the width of the bottom portion of the reinforcing ribs in known wheel covers is generally limited to be within a range of approximately 2/3 to 1/2 of the thickness of the wheel cover main body, with a result that it is difficult to achieve a sufficient reinforcement of the wheel cover main body.